Metal backed pressure-sensitive adhesive



Patented Jan. 18, 1938 PATENT OFFICE amass METAL BACKED PRESSURE-SENSITIVE ADHESIVE Maurice A. Goldman, New Brunswick, N. J., as-

signor to Johnson & Johnson, New Brunswick, N. J., a corporation of NewJersey No Drawing. 1 Application November 7, 1935,

Serial No. 48,793

6 Claims.

The invention relates to adhesive faced flexible strips or fabrics and particularly to sheet materials or tapes having an area or areas thereof coated with a normally tacky or pressure-sensitive adhesive susceptible of and intended for repeated use.

In the surgical and industrial fields it heretofore has been common practice to employ, as a web or vehicle for the adhesive mass or coating, permeable materials such as woven and other textile fabrics, doeskin, leather both natural and artificial, treated or untreated paper in calendered or other form, etc. For some purposes such materials are fairly satisfactory as, for example, where the thickness of the web, its permeability, tendency to contract, and lack of substantial flexibility and contour-fitting properties are relatively unimportant and inconsequential. When, however, the requirements are more exacting and those factors are of consequence, as in masking and insulating under wet environment and solvent exposure conditions, the known .bonding and masking tapes have not been commercially satisfactory. This notwithstanding that there are many avails in the way of so-called waterproof fabrics and that in the paper industry there are on the public commons many grades of paper that are fairly waterproof or, at any rate, fluid-repellent. It so happens, however, that the treatments which they undergo render them undesirably stiff and thick. Quite frequently the chemicals and reagents used in the treatment of the backing were not compatible with the ingredients of the adhesive mass or vice versa, resulting in a reaction which either rendered the mass unstable and .wholly incapable of repeated use and sometimes of any use, or which destroyed or seriously impaired the proof properties of the backing. Even when this condition was not immediately manifest, the known backings, whether treated or not, were objectionable because they lacked the required contour-fitting properties and because of their proneness to mar the work as by disfiguring imprints, embossvments, offsets and other faults difficult to efface and, in any event, adding to the cost. In the case of paper backings and where creping was resorted to in order to obtain a certain order or degree of elongation or an' added measure of flexibility, thecreping made for undesirable twitching or creeping action in the tape which could not be controlled. Moreover, none of the known backings could be trimmed so as to present symmetrically true, clearcut or clean edges devoid of fraying or raveling tendency; all were susceptible to contraction making for lifting and creeping of the tape; there was always an excess of adhesive and consequent squeezing out or flowing of the same beyond the limits of the tape;

the shelf life was comparatively short due to deterioration under changes of climate or exposure to different temperature conditions, and yet there is no way of economically salvaging the backings of spoiled or rejected tapes. There are other faults and disadvantages but it will be sufficient for the purposes of the instant case to rely on those mentioned.

It follows that the desideratum and, hence, the principal object of the invention is to obviate the faults and disadvantages of the known practices and I have discovered that this object may be fully realized by the use of a backing comprised of one or more plies of metal of the nature of foil not alone because of its apparent salvage value but rather largely because it readily lends itself to the purpose inhand and constitutes. an ideal backing for pressure-sensitive adhesive and when so embodied is susceptible of manifold uses other than masking and covering under wet environment and solvent exposure conditions for which primarily it is intended. By the use of a plurality of plies of metal there is obtained an added strength and softness over that present in a single ply of equivalent thickness.

In the practice of the invention I may use any metal or metal alloy capable of being wrought to the desired degree of thinness and still be devoid of cracks, pinholes and other flaws making .for permeability. I prefer, however, to use the softer metals such as zinc, tin, aluminum, etc. because of the relatively low cost of these metals and the facility with which they may be handled in my process as well as their substantial compatibility with adhesive compounds or masses of the pressure-sensitive type.

For some classes of work I may use a single ply of foil,-say, for example, zinc foil of a purity of 9997% and of the order of 1/1000 of an inch thickness, annealed or unannealed. A pressuresensitive adhesive of, for example, the conventional type may be applied directly to a web of foil in any suitable way either as a plastic or in more or less the form of a solution. For example, it may be sprayed, knife spread or applied by coating rolls. And, it here may be remarked that the coated webs or sections thereof may be stacked or rolled and as readily unstacked and unrolled without the intervention of a separating sheet or cloth and without the hazard of promiscuous sticking or of leaving disfiguring marks.

For a better quality of work I prefer to anneal the foil because annealing obviates the tendency of the metal to curl and imparts a desirable measure of softness and ductility. The annealing may be performed in any suitable way and I may anneal the metal in the form of separate and independent plies or as a built-up or laminated structure, all according to the purpose for which the tape is intended. If desired, the annealing may be done on the finished roll. Annealing also has the merit of conferring upon the metal a substantial degree of permanent elongation beyond the elastic limit. There is another advantage in annealing and that is that it is effective in partly removing surface oil or grease, thus, leaving a. clean surface for the application of the adhesive. If the metal is not annealed or whether it be annealed or not, I may sometimes resort to washing or pickling in any suitable way to insure a clean receptive surface.

For ordinary purposes no other treatment of the foil is required to insure proper anchorage coating of the adhesive'. When, however, an especially tenacious anchorage is required or desirable, I pre-treat the receptive face of the foil before applying the adhesive coating. For example, good results may be achieved by mechanically or chemically treating the adhesive receptive face by pitting or stippling it as by sandblasting, chasing or etching. Preferably, how ever, with or without the exercise of such preliminary practices, I apply a priming coat which may be exemplified as follows:

A. Melted rubber-produced by coating the foil with pure rubber, latex or dispersion and heating uniformly to an effective temperature calculated to melt and decompose the coating.

B. Pitch 120 parts, zinc oxide' 126 parts, reclaimed rubber 230 parts, balata gum 50 parts.

C. Pitch 125 parts, zinc oxide 125 parts, reclaimed rubber 250 parts.

D. Reclaimed rubber 50 parts, cumar resin 30 parts, rosin 20 parts.

The invention may be practiced with any appropriate pressure-sensitive adhesive as, for example, the conventional pressure-sensitive adhesive which, as previously stated, may be applied to the primed surface or directly on the metal and in any appropriate way.

From the foregoing it will be apparent that the invention is predicated in the main on the use of an all-metal backing. There maybe occasions, however, when as a matter of convenience or expediency it is desirable, first, to apply the pressure-sensitive adhesive to a non-metal backing and then to invest the latter in a metal backing of the nature of my invention and my inventive thought comprehends this.

While the invention may be practiced with ready formed foil, tapes or sheets, it is preferred to practice it with webs of foil of relatively great area and thereafter to divide the webs to the width and other dimensions required. In the accomplishment of this I may employ any of the usual types of slitting machines. I prefer, however, to use a cutter of the shear type, such machines or devices being more conducive to symmetry of edge finish, and better still, I prefer to divide the web by means of a very thin element heated to white heat. This results in a seared edge and in the case of a built-up or laminated backing of several plies of foil it makes for a unified weld which seals the edges and makes for a symmetrically smooth homogeneous structure. It is obvious, however, that the tape may be slit by mechanical means, of the nature indicated, and subsequently have its edges subjected to a conventional welding operation.

While many of the advantages of the process may be achieved in separate and detailed operations, I prefer to practice it as an unbroken or continuous operation employing as many automatic stages as conditions admit of thereby limiting the number of handlings, reducing to the minimum any tendency towards crystallization, and withal making for and retaining perfection of product.

The new article has certain characteristic qualities which admirably adapt it for masking purposes. Due to its thinness, lacquer has less chance to build up around the edges. Consequently, there is less polishing to be done to remove any ridge remaining. Due to its flatness there is practically 100% adhesion to the surface to which it is applied. Hence, there is no seeping under the edge as is the case with creped tape and, consequently, a better and finer edge remains. No crepingis necessary because the internal strength of the backing is sumcient to withstand rolling or stacking upon itself without lamination. Further, the elongation of the material is such as to make it unnecessary to have creping to assist in the making of curves and to lay fiat after the curve has been made. Because the backing has no fibrous structure a clean, clear edge is present. Such is not the case with cloth, paper, and tape having other fibrous bases. Due to the fiatness of the backing a thinner coat of adhesive can be used. Consequently, no

rough edges will be showing due to the adhesive mass squeezing out as is the case with tapes which necessitate a thicker adhesive mass. Metal backing is impervious and resistant to all lacquer solvents and paint solvents, varnish removers, cleansing agents, and other liquids used in the production of automobile bodies. This imperviousness is inherent and not the result of any treatment of the backing. The backing itself is resistant to moisture and unaffected by climatic changes. Due to its elongation qualities this tape has the unusual and unique ability to take curves and conform to the surface to which it is applied much more easily than is the case with ordinary masking tapes. The elongation of the metal is permanent and there is no tendency towards creeping after it is applied in curved shape, whereas conventional products assume their curves partially by elongation and partially by elasticity, and therefore, tend to resume their normal position by contracting and lifting the edge and create creeping. The metal backing exerts no deleterious influence upon the adhesive compound.

The new article is exceedingly efficient when utilized in the decorative field. It can be applied to any surface and will not mark or mar such surfaceor leave a "ghost. Its thinness, together with the fact that the surface can be embossed, or decorated, or colored, makes it ideal for decorative uses. Its thinness, flatness, conformability, and the fact that the backing is of metal, makes it a very eflicient medium for the hermeti sealing of packages.

The new tape or sheet lends itself readily to use in the field of bottle cap liners. Its use in such field would simplify the mechanical handling of the products as they are handled today and would increase the production facilities of the cap manufacturers. The usual method is concerned with a heat-sensitive adhesive which necessitates makes a very good and suitable backing for surgical tape.

Having described the claimed as new, is:

1. As a new article of manufacture, the combination of a flexible backing comprising one or more plies of metal foil having symmetrically formed selvage edges whereof the salvaging is manifested by hot trimmed seared edges, and a pressure-sensitive adhesive applied as a tenacious coating to said backing and normally prevented from outflow therebeyond by the selvage edges of the backing, said coating having greater adhesion to the backing than to a surface to which it may be applied in service whereby the article is capable of repeated removal and use.

2. The article set forth in claim 1 having the further characteristic that the backing, comprisinvention, what is 'ing a single ply of metal foil, or a plurality of such plies secured as a unit, is heat-treated to confer upon it a substantial degree of permanent elongation whereby it has the unusual and unique capacity to conform, for example, to reverse curves without the hazard of creeping. I

3. A- salvageable article of the removable and reusable type, comprising a strip of metal foil impenetrable to fluids and'having sealed edge margins, said foil being characterized by a marked degree of permanent elongation and a substantially total absence of creeping, combined with a filmiform layer of normally tacky pressure-sensitive adhesive applied to one face of the metal foil and substantially inhibited from flowing Iaterally therebeyond by the sealed margins, said foil having the further characteristic of long life and the ability to withstand the-removal and replacement of the adhesive when the same becomes unstabilized.

4. Method of making articles of the nature indicated, which consists in providing metal foil having the handling qualities of paper, annealing it to confer upon it the property of permanent elongation, and dividing the foil into strips by an operation which substantially will seal the margins.

5. Method of making articles of the nature indicated, which consists in providing metal foil having the handling qualities of paper, annealing it to confer upon it the property of permanent elongation, dividing the foil into strips by an operation which substantially will seal the margins, treating a surface of the foil for the reception of an adhesive, and coating said surface with a filmiform layer of normally tacky pressure-sensitive adhesive. I

6. In the manufacture of articles of the nature indicated, the steps which comprise providing a metal foil having the handling qualities of paper, annealing it, applying a priming coat, applying to the primed surface a fllmiform layer of normally tacky pressure-sensitive adhesive and di-- viding the foil into strips by a trimming operation which substantially seals the margins thereof and prevents outflow therebeyond of the adhesive. I

MAURICE A. GOLDMAN. 

